This invention relates to an improvement in a method for producing ceramic pellet. The method comprises the steps of charging ceramic batch into a longitudinally extending die, pressing the batch in the die between opposing plungers, removing one plunger from the die, ejecting the blank by means of the other plunger and firing the blank. A rotary press has been used to press the ceramic batch by the method described above. The rotary press comprises a plurality of longitudinally extending dies for receiving ceramic batch, means comprising upper and lower opposed plungers for pressing the batch in each of the dies, one of each of the opposed plungers being removable from the die, and the other being movable relative to the blank to eject the latter from the die. The apparatus also includes a rotating table die carrier for the plurality of dies, means at a pressing rotational position of the table for supporting the lower plunger against downward movement, and for driving the upper plunger downwardly to press batch in the die.
In accordance with the instant invention, it was desired to produce a ceramic resistor made of strontium-alumina-copper material disclosed in U.S. Pat. No. 3,959,184, granted May 25, 1976 to Joseph Nemeth. This material, after pressing and firing, should constitute a ceramic resistor with a series resistance between 21K and 38K ohms. Such a resistor is useful as an insert in the bore of a spark plug insulator to suppress electromagnetic interference. After the ceramic resistor material had been pressed in accordance with the method previously described for pressing ceramic batch, that portion of the material in contact with the surface of the removable plunger stuck to the surface as the plunger separated from the material when being removed from the die. As a consequence of the sticking, a majority of the ceramic blanks, after firing, had resistance values which were much higher than 38K ohms.